1. Field of Invention
The present invention is directed to a non-contact position sensor and more particularly to a non-contact position sensor for an actuator or for other settings in which an air gap is required to fluctuate.
2. Description of Related Art
It is often desirable to have a non-contact position sensor when closing a servo loop around an actuator. This becomes difficult in many applications where weight and volume are critical because many non-contact position sensors are implemented using optical devices. If an optical device is not used, then a Hall device is usually chosen.
For similar applications, optical devices are usually large and cumbersome to work with and are often impossible to mount without having the sensor become the device which dictates the volume. Optical sensors need a light source, which also requires volume and extra alignment problems.
Hall sensors have the disadvantage of nonlinearity and must be precision mounted to obtain accurate measurement of position. The Hall sensors also need another component, usually a permanent magnet, for use in sensing position. Another disadvantage of Hall devices is their reaction to permanent and fluctuating magnetic fields.
A final disadvantage of Hall devices and the like is that such devices require a fixed air gap in the motor. In some applications, however, it is required that the air gap fluctuate. For example, one type of actuator for which such devices cannot be used is a linear permanent magnet motor, in which the winding is fixed and the permanent magnet is allowed to move.